Proceedings of the Institution of Civil Engineers Structures & Buildings 158 February 2005 Issue SB1 Pages 21–40 Paper 13310 Received 14/03/2003 Accepted 08/09/2003 Keywords: building structure & design/ concrete structures/seismic engineering Francis T. K. Au Associate Professor, The University of Hong Kong, Pokfulam Road, Hong Kong, China Kun Huang Former Research Student, The University of Hong Kong, Pokfulam Road, Hong Kong, China Hoat J. Pam Associate Professor, The University of Hong Kong, Pokfulam Road, Hong Kong, China Diagonally-reinforced beam–column joints reinforced under cyclic loading F. T. K. Au PhD, MSc, CEng, RPE, MICE, MIStructE, MHKIE, K. Huang PhD, MEng and H. J. Pam PhD, ME, Ir, MHKIE, MIEAust, MIPENZ, CPEng The beam–column joints in a reinforced concrete frame are vulnerable to damage caused by seismic events. The conventional detailing using transverse hoops usually results in serious joint congestion, which creates contruction problems. This paper introduces a new detail especially developed for low to medium seismicity, which involves the use of additional diagonal bars in the joint. Six half-scale interior beam–column assemblies with different joint details, namely ‘empty’, nominal transverse reinforcement and diagonal bars, tested under reversed cyclic loading are reported. The empty joint is not suitable even under moderate seismicity. The test results show that the joints containing the newly proposed detail, with or without axial compressive load present in the column, exhibit better behaviour at the lower range of ductility factors in terms of higher load-carrying capacity, greater stiffness and less strength degradation. Therefore, the newly proposed joint detail is suitable for beam–column joints of reinforced concrete buildings located in regions of low to medium seismic risk. NOTATION A g gross cross-sectional area of the column A S1 cross-sectional area of top beam reinforcement (Eurocode 8) A S2 cross-sectional area of bottom beam reinforcement (Eurocode 8) A sd total area of diagonal steel bars in one direction A sh cross-sectional area of transverse reinforcement in the joint (Eurocode 8) b j effective joint width normal to the plane of beam– column joint C c concrete compressive force acting on periphery of joint from beam (also C 9 c ) C s steel compressive force acting on periphery of joint from beam (also C9 s ) D c compressive force carried by diagonal concrete strut D s diagonal compression field in truss mechanism e 1 , e 2 readings of linear variable displacement transducers to evaluate joint distortion f 9 c compressive cylinder strength of concrete (also f cd according to Eurocode 8) f cu compressive cube strength of concrete f y yield strength of reinforcement (also f yd according to Eurocode 8) h c width of column in the direction of beam h jc distance between reinforcement at two faces in column (Eurocode 8) h jw distance between top and bottom reinforcement in beam (Eurocode 8) L b distance between jacks 1 and 2 L c distance between top and bottom hinges for column l i initial distance between mounting rods for LVDT for evaluation of joint distortion M n nominal flexural strength of beam P compressive axial load applied to the column P 1 , P 2 forces applied by jacks 1 and 2 respectively q behaviour factor (Eurocode 8) T steel tensile force acting on periphery of joint from beam (also T 9) V c column shear force V jh joint shear (also V jhd according to Eurocode 8) V max measured equivalent shear strength of column V n nominal shear strength of column derived from nominal flexural strength of beam V sh bond force from the longitudinal reinforcement of beam V sv bond force from the longitudinal reinforcement of column v d normalized design axial force (Eurocode 8) v j average shear stress in the joint core â initial inclination of LVDTs to horizontal (for evaluation of joint distortion) ª Rd design value of overstrength ratio of steel (Eurocode 8) ˜ peak displacement measured in the test ˜ 1 , ˜ 2 beam displacements at jacks 1 and 2 respectively (upward as positive) ˜ c column drift ˜T c bond force of the part of longitudinal bars overlapping with the concrete strut ˜ y nominal yield displacement ç drift ratio ç u ultimate drift ratio Ł inclination of diagonal bars º factor accounting for the available shear resistance Structures & Buildings 158 Issue SB1 Au et al. 21 Diagonally-reinforced beam–column joints reinforced under cyclic loading
Diagonally-reinforced beam–column joints reinforced under cyclic loading
May 19, 2023
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